Ask JT! the THK FAQ thread

Discussion in 'Terrio HandMade Knives' started by james terrio, Oct 26, 2013.

  1. Chameleonbear


    Aug 14, 2008
    Lay down some knowledge on us! What's the difference between A2, O1, 1095CV, Infi, Elmax and Vanadis? Which would be best(price, edge retention, etc) for a small slicer, by slicer I mean NOT a woods knife but an actual slicer.
  2. james terrio

    james terrio Sharpest Knife in the Light Socket

    Apr 15, 2010
    Well, they're all mostly iron ;)

    1095 and O1 are classic, low-alloy, fairly simple "carbon" steels with very little carbide content. Their greatest attributes are fine grain, which makes them tough and easy to get a very crisp edge on, and the fact that they're inexpensive and easy to work with. They have essentially no corrosion-resistance as we think of it. I prefer O1, 1095CV and 52100 over plain 1095 because they do have a splash of added carbide-forming elements, which help with edge retention without sacrificing toughness or making them difficult to sharpen.

    In the early-mid part of the 20th century, industry started adding more alloying elements like chromium, tungsten, vanadium, molybdenum etc. to steels, mainly in a quest to increase wear-resistance properties and stability at high temperatures ("hot hardness" or "red hardness"... meaning it doesn't lose its temper under stress/friction). This results in what we typically call "tool steels" today. (Not tools as in wrenches and screwdrivers, but cutting tools like mills and drill bits)

    A2 is a very well-known tool steel, not all that different from the simpler steels except that it has around 5% chromium. At those levels the chrome is mostly tied up in carbides, which again adds wear-resistance. D2 is also a tool steel, but it has a lot more carbon and a lot more chrome, which makes for lots more carbides and much better wear resistance - but it sacrifices a lot of toughness.

    INFI is an interesting alloy - as a proprietary alloy, it's hard to really get a handle on exactly what's in it; it kind of depends on whom you ask. But at the risk of over-simplifying things, it's "basically" a high-grade, high-speed tool steel. Although they're quite different chemically, INFI and CPM-3V are very similar in performance, offering a great balance of very high toughness and very good wear-resistance, with moderate corrosion-resistance. Unless corrosion-resistance is a big issue, CPM-3V is my favorite steel.

    Steels like Elmax and Vanadis 4 are really a whole 'nother ball of wax. They have very high levels of alloying elements, and rely on costly third-generation powder metallurgy manufacturing techniques to maintain a fine grain/carbide structure and thereby retain high levels of toughness. They are an outgrowth of "powder" steel technologies that gave us steels like CPM-154 and CPM-S35VN.
    This technology has evolved to such an extent that we now have "stainless" steels like Elmax and CTS-XHP that exhibit excellent edge-retention, can support very fine, keen edges, and levels of toughness that often meet or even exceed those of many plain "carbon" steels.

    For price, you can't beat 1095. For edge retention my choice would be Elmax at 62Rc... which has an added benefit of good corrosion-resistance. But honestly, all these steels will work very well for a pure cutting implement... as long as the geometry is good and the HT is top-notch, you really can't go wrong with any of them.

    Geometry cuts. Alloy selection and HT determine how long a knife keeps cutting.
  3. unit


    Nov 22, 2009

    Well said!, and I'll agree with the following sub-note (if I may tread in your thread):

    Some modern alloys allow for a geometry that lesser alloys cannot support through even a single cut.

    While your eloquent statement technically includes this sentiment, I think it is important to note that, the added expense of the "right" alloy/HT for a user's specific needs/desires (coupled with the "right" geometry) may be more than worth it.

    This balance is rare even in the world of custom knives, and that is a big reason to work with an attentive maker that will take the time to understand his clients.
  4. james terrio

    james terrio Sharpest Knife in the Light Socket

    Apr 15, 2010

    It's also important to take into consideration that the benefits of modern "super" alloys cannot come into play unless they are ground and HT'ed to really take advantage of their superior characteristics. A poorly-ground blade made of excellent steel will not cut as well as a properly-ground blade made of mediocre steel.

    In other words, while it's true that polishing a turd does no good, it's also true that a diamond doesn't really sparkle until it's cut properly.
  5. worldwood


    Sep 30, 2012
    Quote worthy!!
  6. james terrio

    james terrio Sharpest Knife in the Light Socket

    Apr 15, 2010
    Couple more recent questions...

    What if I want mosaic pins on my knife?

    No problem! What I do then is use customized corby bolts hidden under "caps" made of mosaic pin... here's how it works:



    That way you get the cool look without sacrificing mechanical strength. I don't stock a lot of mosaic pins; there are simply too many different ones for me to inventory them all. If you request them, I'll send you links to a couple suppliers and let you pick out the ones you prefer.
  7. james terrio

    james terrio Sharpest Knife in the Light Socket

    Apr 15, 2010
    Do all the finishes cost the same? Are there any benefits of one finish over another finish?

    No; a machine finish is the least expensive. Hand-satin and "silk polish" cost a bit more because they require a lot more
    hand work. The finer the finish, the nicer it looks, but more importantly, the steel resists corrosion better. My most popular finish is a basic hand-satin at 600 grit, because it's easy to keep clean and doesn't tend to show small scratches from use.

    I should ask the question, what is your return policy? If I get it, and for some reason it is not what I wanted, how do we handle that?

    I warranty all my work against defects in craftsmanship and materials, but unfortunately I cannot warranty against matters of taste. I try to be very clear about specs, materials, designs features etc. Especially in the case of custom orders, once my drawings/photos are accepted and approved, I consider that a contract to be honored.

    I have yet to have a single client return a knife to me.

    As your knife gets scuffed up and grungy from lots of use, I'll happily clean it up, sharpen it and bring it as close to new condition as practical. Just send it to me with return shipping, no charge for labor.
  8. Jonny1280

    Jonny1280 Gold Member Gold Member

    Jan 5, 2012
    Hi James,
    I've always been curious to know at what temperature would it take to start affecting the heat treat of a blade.
    I've heard varying answers from hot water to 500 degrees.
    I know hot water will not affect a good heat treat. But how hot is too hot when comes to ruining/affecting the HT.
    I'm sure it would depend on the temperature used to HT the knife in the first place...right?

    What are your thoughts?
  9. james terrio

    james terrio Sharpest Knife in the Light Socket

    Apr 15, 2010
    Even boiling water isn't going to harm a heat-treated blade unless you put it back in a leather sheath still wet.

    Let's back up a step... at its most basic, heat-treating involves the following:

    Hardening steel is accomplished by heating it up to at least 1550F and quenching it quickly enough that it develops the most hardness it can get. The temperature required goes up to around 2000F for steels with a lot of alloying elements, and the chemical composition affects how quickly it needs to be quenched as well. Regardless, this as-quenched structure is brittle and unstable.

    Tempering steel is done after hardening/quenching to relieve stress, stabilize the structure of the steel, and take out some of the hardness and brittleness. This generally requires temperatures of at least 400F; again, depending on alloy content temps as high as 900F may be used. This results in steel that's much more tough.

    So the upshot is, anything less than 400F is very unlikely to harm a finished blade.

    The trouble comes when grinding or aggressively sharpening (even on dry stones) hardened steel, because thin sections like edges and tips can very quickly reach temperatures far in excess of 500F. Such operations require a light touch and near-constant cooling to prevent heat build-up. You can't rely on the steel changing color or your fingers feeling hot to warn you of this happening... by then the damage is already done.

    Overheating the edge on HT'ed steel can actually re-temper the steel to such a point that it's too soft to hold an edge properly, and in the case of some air-quenched steels could actually make them more brittle and weak. Google a cat named Roman Landes for more in-depth discussions of how fast this can happen.

    There are several well-known knife companies (who shall remain nameless here) that have had "bad" batches or examples of knives that won't hold an edge worth a hoot for this very reason - grinding too fast. The good news is that in many cases, the damage only goes into the steel a very shallow ways, so re-sharpening properly can get you back to properly-tempered steel.

    These considerations are why I almost always prefer to fully grind my bevels before HT, and then afterwards barely set my edges on a grinding belt, until I jusssst about reach an apex... then finish sharpening them on stones with a light oil or lube (water is fine if you're using diamond "stones" or waterstones). That's the best way I know to prevent those problems from ever happening.
  10. Jonny1280

    Jonny1280 Gold Member Gold Member

    Jan 5, 2012
    Thanks for 411 Mr. Terrio!
  11. james terrio

    james terrio Sharpest Knife in the Light Socket

    Apr 15, 2010
    No problem, it's just part of my job :)
  12. worldwood


    Sep 30, 2012
    This thread is a great resource and getting better all the time, thanks for sharing your knowledge once again James.

    Im just curious, whats the biggest knife you have made?

    What can i say i like em big :D
  13. james terrio

    james terrio Sharpest Knife in the Light Socket

    Apr 15, 2010

    The larger of those two has an 11" blade; the smaller, only 9"
  14. james terrio

    james terrio Sharpest Knife in the Light Socket

    Apr 15, 2010
    That's very kind of you to say! I stand humbly on the shoulders of giants, and can only hope to continue their work, or at least be respectful of it in my own way.

    There is a THK prototype in the works that will dwarf both those knives above... not necessarily in size or weight, but in performance.

    Stay tuned for updates. ;)
    Last edited: Mar 6, 2014
  15. worldwood


    Sep 30, 2012
    those are badass man!! Cant wait to see the new one!!
  16. james terrio

    james terrio Sharpest Knife in the Light Socket

    Apr 15, 2010
    It's gonna be pretty cool, I think. It will involve a compound grind... full-flat near the handle for whittling and stuff, and convex
    near the the tip with a slightly thicker edge for heavy chopping. The challenge is to build it stout enough for serious work, but balance it so that it doesn't tire you out in use.

    In other news...

    To date, I've been using 5/16" OD, roughly 1/4" ID stainless tubing to line my lanyard holes... that allows for a single piece of 550 cord to be passed through.

    What if I want a thong/lanyard tube with a larger inside diameter?

    I was asked this the other day, because the client wants to be able to pass 2 thicknesses of paracord through the tube to suit his preferred style of lanyard.

    I can make that happen! I'll be sourcing different sizes as well as wall-thicknesses to provide more versatility in that regard. As I move forward with new knives, I'll offer a wider range of tube sizes as a no-cost option. :thumbup:
  17. james terrio

    james terrio Sharpest Knife in the Light Socket

    Apr 15, 2010
    More questions from e-mail...

    Is there a stabilized wood, or other wood (desert iron or something) that you would recommend aesthetically for a handle. Or does that "weaken" the "survival" aspect of the knife?

    For knife handles, there is nothing more pleasing to my eye than highly figured wood. Many species like desert ironwood, curly/birdseye maple, crotch walnut and cocobolo are both beautiful and quite strong/stable. Burls and spalted woods of various types absolutely must be professionally stabilized for use on a knife. They're just not very strong in their natural state.

    It's important to remember that figured wood (stabilized or not) is a natural material with voids and grain structures that do not lend themselves to ultimate durability. They also require a reasonable amount of care and can darken over time and with exposure.

    If maximum durability and very low maintenance is a priority, my choice is G10 every time.

    When a client's desire for beauty, good durabilty and moderate maintence is tempered with an understanding that I cannot absolutely guarantee that such a handle will not shrink/swell with the passage of time or break apart under heavy impact, I can and do use quality hardwoods with confidence.

    How much more would it cost for something like that?

    That's a tough question to answer, because there are so many factors involved. Walnut and maple are relatively inexpensive, but they require a good deal of labor and time to seal properly... ironwood and cocobolo are more costly, but they're pretty much ready to use as-is without a lot of finishing work... professionally-stabilized burls and spalted woods cost a lot more at the outset, and every now and then I run into a piece that has a nasty hidden flaw I simply can't fix. Which means starting over... :grumpy:

    In short, wood handles that I'm comfortable putting my reputation behind are going to cost more than micarta or G10.

    How much more varies widely.

    As a sidenote, I have zero faith in various DIY/home methods of "stabilizing" wood. I only use pieces from highly respected professional firms.
  18. james terrio

    james terrio Sharpest Knife in the Light Socket

    Apr 15, 2010
    Please also see this thread in ShopTalk for a thought-provoking discussion about heat build-up and sharpening, with input from several makers and enthusiasts. :thumbup:
  19. worldwood


    Sep 30, 2012
    Thanks for that Link JT, lots of great info there and i learned some stuff!!!
  20. james terrio

    james terrio Sharpest Knife in the Light Socket

    Apr 15, 2010
    Do flat grinds perform better than convex grinds?

    Well... that depends on what kind of performance you need. I make both styles. Here's a simple graphic showing the difference:

    (Not to scale, and simplified for the sake of clarity...)


    Given the same stock thickness, a convex grind obviously leaves more steel in the blade, resulting in a knife that's stronger overall. Convex grinds also tend to push the material being cut out of the way, and are less likely to bind up halfway through a challenging cut. In extreme cases (very pronounced curvature), convex grinds cut to start with, and act more like a splitting wedge as they pass through tough materials. If you require maximum strength and plan to put your THK to hard use, a convex grind is the way to go. Convex grinds are an excellent choice for heavy-duty/tactical/survival knives.

    Flat grinds are better at pure slicing, simply because they are thinner behind the edge. If you prefer maximum keen-ness and expect your knife to make precise cuts, a full-flat grind is my recommendation.

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